An inflator for an inflatable vehicle occupant protection device, such as an air bag, may include a container storing pressurized inflation fluid. The container has an outlet opening which is closed by a rupturable closure wall.
In addition to the inflation fluid, the container may store ignitable material for heating the inflation fluid. Such an inflator has an igniter containing a small charge of pyrotechnic material. A bridgewire in the igniter extends between a pair of electrodes in a heat transferring relationship with the pyrotechnic material. When the air bag is to be inflated, an actuating level of electric current is directed between the electrodes through the bridgewire. This causes the bridgewire to become resistively heated sufficiently to ignite the pyrotechnic material. The pyrotechnic material then produces combustion products which, in turn, ignite the ignitable material stored in the container.
The fluid pressure inside the container is increased by the heat generated upon combustion of the ignitable material. When the increasing fluid pressure reaches a predetermined elevated level, it ruptures the closure wall. The inflation fluid then flows from the container through the outlet opening and into the air bag more quickly than if it had not been heated and further pressurized.
Welds are used to connect the bridgewire electrically between the electrodes in the igniter, and also to fix and seal the closure wall across the outlet opening. Accordingly, it may be desirable to examine and evaluate the bridgewire welds to ensure that ignition of the ignitable material will be achieved reliably. Likewise, it may be desirable to examine and evaluate the closure wall welds to ensure that the appropriate elevated fluid pressure levels can be attained prior to rupturing of the closure wall.